The present invention relates to an electrode additive comprising an electrochemically active material in a form of one-dimensional molecular chain, wherein the electrochemically active material is contained inside a nanotube-formed conductive shell material. The present invention further relates to an electrode comprising said electrode additive, and the uses of said electrode additive and said electrode.
Owing to the high capacity, low cost, and abundant features, sulfur used as the cathode of lithium batteries has long fascinated the scientific community. Orthorhombic S8 is the most stable allotrope and widely used in the current Li—S batteries. However, S8 is insulating and a conventional Li—S battery based on cyclic S8 molecules usually discharges according to the two-electron reaction ⅛S8+2Li++2e−↔Li2S, which brings about two plateaus. Since the polysulfides generated in the discharge process may be dissolved into the electrolyte and then deposited onto the lithium anode during the charge process, the sulfur cathode may suffer from a severe capacity fade.
Some former researches have found that one-dimensional chain-like sulfur as another allotrope shows a distinct electrochemical behavior, but it is instable in structure and therefore cannot exist independently.